On the wear behaviour of silicon nitride sliding against metals in water

Purpose - Testing of silicon nitride (Si3N4) or silicon carbide (SiC), sliding on itself in water, revealed that hydrodynamic lubrication can be obtained at low-sliding velocity. The purpose of this paper is to study the performance of Si3N4-metals pairs, sliding in water. Design/methodology/approach - Ball on disc unidirectional sliding tests are run with Si3N4 against tool steel, stainless steel and cast iron in water. The friction force is recorded continuously and the wear is evaluated at the end of the run by geometric technique. In addition, SiC sliding on itself in oxidant solution (3 per cent solution of CrO3 in water) is tested. Findings - The measured friction and wear of water-lubricated Si3N4 against metals are higher compared to Si3N4 sliding on itself. At the end of the run-in SiC, lubricated by the oxidant solution, obtains hydrodynamic lubrication and friction and wear are lower than in water-lubricated SiC. Research limitations/implications - The experimental results obtained are valid within the range of load and sliding velocity applied 1-10 N, 0.04-0.33 m/s, respectively. The Si3N4 sliding against metals in water over sliding distance of 3,000 m has not shown tendency towards hydrodynamic lubrication. Originality/value - The paper presents test data on friction and wear properties of Si3N4 sliding against metals in water. The low friction and ball wear rate of the SiC, lubricated by the oxidant solution, shows the potential of the 3 per cent distilled water solution of CrO3 to surpass water as a lubricant for SiC sliding bearings.